os_arch values no longer match hugo releases

[TheTedAdams]

https://github.com/stackb/rules_hugo/blob/master/hugo/internal/hugo_repository.bzl#L15-L21

os_arch = repository_ctx.attr.os_arch

os_name = repository_ctx.os.name.lower()
if os_name.startswith("mac os"):
    os_arch = "macOS-64bit"
elif os_name.find("windows") != -1:
    os_arch = "Windows-64bit"
else:
    os_arch = "Linux-64bit"

The os_arch options in hugo_repository() no longer aligns with the ones being used in hugo releases:

This means for recent releases I believe only linux is actually working. Supplying os_arch manually also doesn't seem to work, as we are overriding it whether or not it was provided.